A radical change may be underway in the way journalists cover court cases, thanks to a court of appeal ruling earlier this month.

The latest version of the Criminal Procedure Rules, which came into force last October, entitles any member of the public to apply to read or copy documents referred to in court cases. Following the appeal, in which the Guardian sought access to documents referred to in the Tesler extradition case hearing, the presumption will now be that such requests should be approved unless there is a good reason not to.

This is a big deal, for a number of reasons. As in the civil courts, the amount of paperwork involved in criminal cases has gradually grown in order to reduce the need to argue everything out orally in front of a judge. Given the pressures courts operate under, that clearly makes sense. But as the percentage of information made available to the press and public drops, so too does the ability of observers to understand what is going on.

I've lost count of the number of times I lost track of a prosecutor's case because he started referring jurors to photographs, maps and records I simply can't see. Or given up on an inaudible police interview tape because I'm the only one in court lacking a transcript. But now we have what seems to be a concrete legal basis for demanding access to these documents.

Outraged by a district judge's refusal to allow them to see the various bits of paperwork used in the Tesler extradition hearing, the Guardian applied to have the decision overturned at the high court. They lost, but that ruling was reversed on appeal. The kicker is found at paragraph 85 of Lord Justice Toulson's leading judgment: "In a case where documents have been placed before a judge and referred to in the course of proceedings, in my judgment the default position should be that access should be permitted on the open justice principle; and where access is sought for a proper journalistic purpose, the case for allowing it will be particularly strong."

If these documents are seen by a judge or jury, and used to decide matters affecting someone's liberty, why shouldn't they be out in the open?

So far, we've had mixed results, and getting judges to accept that line of reasoning has been an uphill battle. Using the new case, I recently asked for press access to all jury exhibits in an ongoing murder trial at the Old Bailey. The judge refused, saying a "blanket application" was "far too general to be appropriate", and suggested he thought disclosure could only ever safely be made after a verdict.

In the inquest into the death of the Mi6 employee Gareth Williams, counsel instructed by the press managed to get the coroner to direct that any "exhibit or court document be disclosed to the media". That was great, until we noticed her saying pointedly, after every document was read, that only the portion read aloud was evidence - the documents themselves were "not exhibits".

Quite a bit of this is can be put down to a sort of culture shock; courts have seldom, if ever, been asked to be this open before. Reading between the lines, there is a predictably mundane reason behind the initial slow progress: they don't have spare copies of anything.

While your dentist probably ditched paper records long ago, the courts of the 21st century remain deeply cautious about IT. Admittedly, they schedule cases electronically using software from the early 1990s, and it is now common for barristers in particular to email judges directly. But, in almost all cases, the actual written evidence is on paper - lots and lots of paper.

Ironically, almost all of these documents have been printed from digital versions held by the parties. Even without producing extra copies for the media, this must cost a fortune - and probably explains at least some of the official reticence .

Whether or not the Tesler ruling has any practical effect across the legal system will mostly depend on what action the courts and Crown Prosecution Service take. Right now, the CPS are quietly waiting to see what judges in the lower courts will require of them in practice before committing to any new policy of their own.

If they continue to dawdle, the results will be inconsistent at best. Few of us have the resources to bring a judicial review, so to a great extent we're at the mercy of their goodwill. My suggestion to the courts would be to introduce a system in which one copy of every document given to the judge or jury is held in a separate file for the public. The promised digitalisation of criminal trials could achieve the same thing, but in a far less expensive way.

Despite these early disappointments, it can work. The day after the judgment, I was allowed to read witness statements at a crown court hearing. No lawyer had allowed me to do that before - ever. Clearly, there are solicitors and barristers out there who share our desire for transparency. Will that be enough?